In the past, most buildings, especially houses, were built with separate heating sources for domestic hot water and household heat. This included separate energy conversion units and segregated distribution systems, namely separate gas or oil burners or electric elements; separate sets of controls, namely separate thermostats, thermocouples, electric valves and regulators; separate hot water storage tanks, and separate conduits for transferring the heated water. It is readily apparent that there is a great deal of duplication of common components leading to inefficient generation of heat energy, duplicate loss of heat through storage tanks, and wasted space.
One solution is to utilize a tankless, on-demand water heater to provide hot water, thereby eliminating some of the wasted space and duplication of hot water storage tanks. These systems tend to be more energy efficient because tank stand-by heat loss is eliminated. These tankless systems, however, typically determine the water heating requirements by summing the maximum demands for hot water for domestic use and for household heat. Thus, in order to adequately meet the high priority demands for maximum domestic use while there is also a maximum demand for hot water for household heat, an excessive capacity for heating the water is usually required, but seldom used. Moreover, these systems use dual heat exchangers with separate conduit loops to separately heat different water for sinks and for space heating purposes. This all results in an excessively high capacity heating unit, inefficiently uses the heat source, requires an unduly large system and is unduly expensive.
The system of the present invention provides the benefits of a tankless water heater, yet permits use of a smaller capacity heater by incorporating it into a system using a flow detector. This system uses a single source of water having a single heat exchanger to heat all water and to use only that heated water for both domestic household use, such as the hot water faucets and showers (a high priority), and for heat for the house (a lower priority). The single instantaneous heat source using a single heat exchanger eliminates the waste of energy occurring when separate heat sources and separate distribution systems are employed or heat is lost through one or more water storage tanks, and eliminates the waste of space required by multiple storage water tanks and conduit loops. However, in order to effectively provide hot water for domestic use when there is a simultaneous demand for heat, assuming domestic use is of a higher priority, the flow of hot water must be detected and regulated. This is done by reducing the hot water supply to the water to air heat exchanger of the heating system when the demand for hot water for domestic use exceeds a predetermined threshold. Such an interruption in the hot water supply for heating the house is usually of little consequence because the loss of heat by a house is very slow, and a short interruption is barely, if at all, perceptible. The present invention uses a fluid flow rate detector which controls an electric switch. The switch may be placed in series with a pump that regulates the water flow to the heat exchanger.
With respect to systems providing a source of hot water and a source of household heat from a single source, an exemplary system is shown in U.S. Pat. No. 4,178,907 to Sweat, Jr. However, the system does not utilize a flow rate detection device to detect, regulate, or prioritize the flow of fluid to the hot water faucets or sinks and to the house heating system. Moreover, the system does not utilize an instantaneous source of heat for the water.
In the past, it also has been known to utilize various flow actuated control devices to adjust the flow of fluid. Exemplary devices are illustrated in U.S. Pat. No. 2,963,563 to Patterson, U.S. Pat. No. 4,313,111 to Anderson, U.S. Pat. No. 4,497,434 to Lawless, and U.S. Pat. No. 4,513,184 to Hughes. However, there is no disclosure of the use of any of these control devices to prioritize the flow of hot water from an instantaneous heat source between hot water sinks and a water to air heat exchanger for space heating.
It is, therefore, an object of the present invention to provide a heating system having an instantaneous source of hot water for both a water sink and for a water to air heat exchanger, and a fluid flow detector to govern fluid flow to the water sink and heat exchanger. These and other objects and advantages of the invention will be particularly identified below.